Referenced in: none

Automatically associated channels: BKβ , Slo1

Title: Magnesium lithospermate B dilates mesenteric arteries by activating BKCa currents and contracts arteries by inhibiting K(V) currents.

Authors: Hai-fei Zhang, Xue-Qing Chen, Guo-yuan Hu, Yi-Ping Wang

Journal, date & volume: Acta Pharmacol. Sin., 2010 Jun , 31, 665-70

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/20453873

Abstract
To examine the involvement of K(+) channels and endothelium in the vascular effects of magnesium lithospermate B (MLB), a hydrophilic active component of Salviae miltiorrhiza Radix.Isolated rat mesenteric artery rings were employed to investigate the effects of MLB on KCl- or norepinephrine-induced contractions. Conventional whole-cell patch-clamp technique was used to study the effects of MLB on K(+) currents in single isolated mesenteric artery myocytes.MLB produced a concentration-dependent relaxation in mesenteric artery rings precontracted by norepinephrine (1 micromol/L) with an EC(50) of 111.3 micromol/L. MLB-induced relaxation was reduced in denuded artery rings with an EC(50) of 224.4 micromol/L. MLB caused contractions in KCl-precontracted artery rings in the presence of N-nitro-L-arginine methyl ester (L-NAME) with a maximal value of 130.3%. The vasodilatory effect of MLB was inhibited by tetraethylammonium (TEA) in both intact and denuded artery rings. In single smooth muscle cells, MLB activated BK(Ca) currents (EC(50) 156.3 micromol/L) but inhibited K(V) currents (IC(50) 26.1 micromol/L) in a voltage- and concentration-dependent manner.MLB dilated arteries by activating BK(Ca) channels in smooth muscle cells and increasing NO release from endothelium, but it also contracted arteries precontracted with KCl in the presence of L-NAME.